Structural Properties and Torsional Dynamics of Peroxides and Persulfides

Abstract

For the study of molecules containing O—O and S—S bonds, an analysis on the effect of level of theory and basis sets on electronic properties and geometrical parameters for H2O2 and H2S2 was done. Substitutions of one or both hydrogens in these molecules either by halogen atoms or alkyl groups were investigated for properties like geometries, dipole moments, cis and trans barriers. Attention has also been dedicated to the study of energy levels in the very anharmonic torsional potentials, obtaining their distributions as a function of temperature and partition functions for the torsional motion, of relevance for the isomerization rate leading to exchange between chiral enantiomers. Estimated rates both for underbarrier tunnelling and overbarrier transitions are consistently smaller for the S—S cases with respect to the corresponding O—O ones, due to the generally higher barriers. Regarding intermolecular interactions, of specific importance for collisional chirality exchange, an exploration was done for both H2O2– and H2S2–rare gases systems, extending the joint experimental and theoretical approach already tackled in this laboratory for interactions of H2O and H2S with the rare gases.